There is a continuing interest in the preparation of synthetic fragrance and flavor components and their use in consumer products. Thiols, which are traditionally associated with strong unpleasant odors, can, in certain cases, also be used to impart fruity notes in both flavor and fragrance compositions.
Specific thiol materials for use in flavor and/or fragrance have been disclosed. U.S. Pat. No. 6,878,366, discloses ethyl 3-mercaptobutyrate as a flavor and fragrance material. The compound is prepared from ethyl crotonate and sodium hydrogen sulfide to make the disulfide dimer, which is then reduced to the free thiol.
U.S. Pat. No. 5,565,473 describes the synthesis of ethyl 3-mercapto-2-methylpropanoate and ethyl 3-acetylthio-2-methylpropanoate by thiolacetic acid addition to 2-methyl-2-propenoates. Nielsen and Madsen, Tetrahedron Asym. 1994, 403-410 describe thiolacetic acid addition to ethyl crotonate, followed by deprotection to the free thiol; also for thiolacetic acid addition to methyl crotonate see Hutchinson et al., J. Med. Chem. 1994, 1153-1164. Additions to various methyl butenoates by protected thiols are described in Miyata et al. JOC 1991, 6556-6564; Miyata et al. J. Chem. Soc. Perkins Trans. I. 1993, 2861-2862; Nishimura et al. JOC 2002, 431-434 (phenylthio additions) and Lee et al. Synth. Commun. 1996, 2189-2196 (hexylthio addition to methyl 2-methylbutenoate).
U.S. Pat. No. 7,105,194 discloses 3-mercapto ethyl esters of hexanoates. U.S. Pat. No. 6,899,911 discloses ethyl 4-(thioacetoxy)butyrate as a flavor material. U.S. Published Application No. 2009/232747 claims various ethyl 2-sulfanyl-2-methylpropanoates for use as flavor and/or fragrance materials. U.S. Pat. No. 6,610,346 describes benzyl mercaptan addition to methyl tiglate to yield methyl 3-benzylmercapto-2-methylbutanoate as an intermediate in the synthesis of fragrance materials. JP03074351 describes the preparation of methyl 2-methyl-3-phenysulfinylbutanoate.
International Published Application No. WO 2005/082346 discloses methyl 3-acetylthio-2-methylbutanoate, which is described as a drug intermediate. The free thiol of the free acid, 3-mercapto-2-methylbutanoic acid (chiral) is also described therein as a synthetic intermediate. U.S. Pat. No. 7,071,175 discloses 3-mercapto-substituted carboxylic acids in drug synthesis.
There remains a need and demand for unique fragrance and flavor compositions. There is also a need for more efficient synthesis techniques to prepare components, particularly thiol-containing compounds, for fragrance and flavor compositions.